Physics Help Forum Physical chemistry - nernst equilibrium potential

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 Mar 14th 2017, 02:29 PM #1 Junior Member   Join Date: Mar 2017 Posts: 2 Physical chemistry - nernst equilibrium potential Hey you all! I am taking a neuroscience class and am struggling with the Nernst equation. I am doing something wrong, because I never seem to get the answer right. Here is the question, and sorry if I am posting this in the wrong threads: Calculate the reversal potential of a calcium selective conductance at 37 Celsius if the intracellular calcium concentration is 1 uM and the extracellular calcium concentration is 2 mM. I am assuming I have to convert 1 uM to mM... would be 2000 mm? I have tried this: E CA +2 : RT over ZF x IN (Ca+ 2 over 1) = 8.314 Joules over +2 times 310.15 over 96.500 I keep getting wrong numbers when calculating: The multiple choice answers are as follows: 1. - 90 mV 2. - 103.5 mV 3. 101.5 mV 4. 203.0 mV My guess is -103.5, but I don't just want to be guessing. I want to know how to do the equation properly and how to get the correct answer. PLEASE HELP?! THANK YOU!!
 Mar 14th 2017, 03:02 PM #2 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 926 You have the unit conversion the wrong way round. 1 millimole = 1000 micromoles. Are you also using absolute temperature for T, not degrees Celsius? topsquark likes this.
 Mar 15th 2017, 03:10 PM #3 Junior Member   Join Date: Mar 2017 Posts: 2 Hey, thanks for the reply!! Oh wow, i had no idea I had the conversion wrong. thanks for that. So, if 1 = 1000 mm , would i have to convert the 2mm? I did convert Celsius to Kelvin. 37 = 310.15K

 Tags chemistry, equilibrium, nernst, physical, potential

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